1. Field of the Invention
The invention relates to the field of video display terminals, and more particularly to a mechanism for moving the display of a video display terminal periodically along a path which varies the distance from the display to a viewer, thereby contributing to the relief of eyestrain and the like. More particularly, the invention concerns a compact position varying mechanism which can be incorporated into or mounted under a standard display of a video terminal such as a computer work station.
2. Prior Art
Numerous instances of physical complaint including but not limited to eyestrain, muscle strain, mental fatigue, headaches, stress, sore necks and sore backs and even increased spontaneous abortion rates of pregnant females have been reported by viewers who are required by their jobs to maintain a position in front of a display terminal for many hours each day. Typically, the display of a video terminal is placed immediately adjacent the terminal keyboard, which is usually within the user's reach, thus placing the display rather close to the viewer, in a fixed position. Television viewers who intently watch the screen for long periods for business or for pleasure are also potentially subject to such problems; however, television viewers are not limited to a location within reach of the display and typically station themselves farther from the display than do video terminal users. Among those whose occupations require long term close attention to a display screen of a video terminal include, but are not limited to, stock brokers, typists, word processors, scientist, engineers, data entry persons, computer programmers, students, traffic controllers, telephone order takers, etc.
Long term focusing of the eyes at a fixed, relatively close location may tire the focusing muscles in the viewer's eyes and can cause conditions of myopia (nearsightedness), hyperopia (farsightedness), amblyopia (lazy eye), presbyopia (aging process or eyestrain), learning disabilities from poor vision perception, accomodation (focussing), convergence (centering), strabismus (wandering eye), monocular/binocular vision imbalances, muscle and nerve imbalances or inability of the eye to focus effectively at near and far distances. In order to rest the eye muscles, persons will frequently look away from the screen to focus at some more distant point. With age, many persons find it difficult to change focus rapidly between a distant point and a nearby point, requiring correction via bifocal lenses. However, it is widely accepted that individuals subject to such problems can improve their vision by exercising the eye muscles, i.e., by focusing sequentially at different distances. An optical instrument to carry out this type of exercise is disclosed in U.S. Pat. No. 4,294,522--Jacobs. An instrument to relieve eyestrain in television viewers is disclosed in U.S. Pat. No. 3,813,419--Pennar. Pennar teaches a linearly movable television platform which is supported on a pair of parallel axles extending transversely to the direction of movement. Pennar provides a drive motor connected for rotating one of the axles.
Users of video display terminals can benefit from a device which requires them to exercise the focusing muscles of their eyes during periods of display terminal observation. Moreover, the users will be more comfortable if they are not fixed physically in a particular body position for long periods. Eye exercise and the ability to shift in position comfortably can be obtained by changing the distance and direction of the display terminal from the viewer, particularly in connection with a work station which permits the user to vary the position of the keyboard as well. However, there are certain practical problems encountered in the design and configuration of an apparatus to accomplish these objectives. The apparatus must be compact, and have a relatively low profile, such that the display can be located in an optimal beneficial position. Whereas at least a motor is required in a linear actuator for moving the display, and a typical motor and the mounting means therefor require several inches of height, as shown by Pennar, it is difficult to conceive of a practical device which can move the display without occupying undue space. Furthermore, the mechanism must be extremely smooth and quiet, because any noticeable vibration or movement of the display or noise is irritating and distracting. In short, the mechanism must be all but invisible or transparent to the user, occupying minimal space and operating such that the changing position of the display occurs substantially without the user even noticing that this has occurred.
The present invention provides a mechanism for moving a video display terminal in a periodic path with respect to the viewer, thereby requiring the viewer's eyes to focus at varying distances as the display is moved. The mechanism preferably comprises a base and relatively movable platform, with a motor disposed at the rear of the base, coupled to the shaft of a linear actuator having a low pitch bidirectional helical path for carrying a follower linked to the platform. The height of the apparatus is minimal (e.g., hardly more than the diameter of the actuator shaft plus the thicknesses of the base and platform) and the mechanism is smooth and quiet. The positioning apparatus can be arranged to allow the viewer to select certain parameters of operation, such as the period of displacement or the amplitude of the displacement. The entire package is arranged for minimal effect on the configuration and operation of the video display terminal, while achieving the desired periodic or cyclical displacement of display position.